SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Journal of dance medicine & science : official publication of the International Association for Dance Medicine & Science

23

Turnout in classical dance refers to the external rotation of the lower extremities so that the longitudinal axes of the feet form an angle of up to 180°. To what extent a myofascial manipulation (myofascial release, MFR) could enhance this external rotation is as yet unknown. In this pilot study, 16 students of dance and 3 dance instructors were randomly assigned to an intervention group (IG; N = 10) and a group of controls (CG; N = 9). Isolated external hip rotation (EHR) and functional turnout (TO) were evaluated three times (pre-, post-, and follow-up measurement) using a plurimeter and Functional Footprints® rotation discs. In addition, subjectively perceived physical flexibility (PPF) was determined by means of a written survey. The interval between pre- and post-measurement and between post- and follow-up measurement was 4 weeks. Only the IG received four 20-minute MFR treatments of the lower limb at weekly intervals between pre- and post-measurement. In both the post-measurement (pre- versus post-: p = 0.038, d = 0.77) and the follow-up measurement (pre- versus follow-up: p < 0.001, d = 1.66) the IG showed a significantly improved isolated EHR of the right hip and a significantly increased PPF (pre- versus post-: p = 0.047, d = 0.73; pre- versus follow-up: p = 0.012, d = 1.00). The left EHR as well as the right and left TO were not affected by the intervention. It was demonstrated that four sessions of MFR of the lower limb can induce an improvement in the isolated external hip rotation (right hip). The beneficial effects of the treatment regarding an improvement of functional turnout could not be entirely verified in this pilot study. However, the significant increase in the participants' subjective flexibility supports the promising trend in the objective parameters and emphasizes the need to undertake further research.

Concepts: Left-wing politics, Right-wing politics, Political spectrum, Limb, Human leg, French Revolution, External rotation, Classical ballet

23

The purpose of the present study was to investigate the influence of instructions promoting an external versus internal focus of attention on the learning of a specific balance task, the pirouette en dehors (from fourth position), in 10-year-old novice ballet students. In addition, we sought to gain insight into learners' motivation and subjective learning experience as a function of different focus conditions. Thirty-eight children were randomly assigned to one of two groups. In the external focus (EF) group, participants were asked to focus on a spotting point on the wall in front of them for as long as possible. In the internal focus (IF) group, participants were asked to focus on the initial position of their head relative to the wall in front of them and on keeping it in that position for as long as possible. The task goal was to rotate as far as possible, and the dependent variable was the number of degrees rotated. All participants performed 15 practice trials of a (right) pirouette. Two days later, participants completed retention and transfer (left pirouette) tests without attentional focus reminders. After the practice phase, participants were asked what they thought about while practicing the pirouette and completed self-rating scales related to their perceived competence, effort, and sense of the importance of doing well. The EF group demonstrated superior performance relative to the IF group during practice, retention, and transfer phases. In addition, EF participants' responses indicated higher perceived competence and greater satisfaction with their performance, as well as greater importance of performing well. In contrast, IF participants reported more nervousness and fear of losing balance and not doing well. Overall, the findings demonstrate that external relative to internal focus instructions enhanced the students' learning of the pirouette en dehors and had positive motivational consequences.

Concepts: Psychology, Attention, Sense, Performance, Binary operation, Rotation, Focus, Classical ballet

23

The purpose of this study was to evaluate the midfoot longitudinal arch height and correlate it with active hip external rotation (ER) in dancers during static postures and technical steps of classical ballet (i.e., first position, demi-plié, battement fondu à la seconde, pas jeté à la seconde, and grand jeté à la seconde). A 3D motion analysis system was used for kinematic analysis. The arch height was significantly reduced during the battement fondu à la seconde, pas jeté à la seconde, and grand jeté à la seconde when compared to standing (p = 0.000 for all comparisons), first position (p = 0.000, p = 0.000, and p = 0.001, respectively) and demi-plié (p = 0.015, p = 0.003, and p = 0.006, respectively). No significant correlation was found between arch height and active hip external rotation (p > 0.05). Hence, active hip external rotation does not seem to be related to midfoot pronation in this sample. Other factors, such as intrinsic and extrinsic foot muscle strength, may be related to the midfoot arch height. These findings contribute to a better understanding of ballet steps, but future studies are required to clarify this topic completely.

Concepts: Foot, Muscle, Correlation and dependence, Classical mechanics, Intrinsic and extrinsic properties, Ballet, Classical ballet, Ballet technique

21

Overuse injuries in dance are extremely common and often difficult to treat. High training load and dancing with pain are frequently regarded as risk factors for musculoskeletal injuries in professional dancers. The aims of this study were to assess for: 1. any association between training load (TL) and symptoms of overuse injury in professional dancers, and 2. any difference between the number of “time-loss” injuries and injuries causing significant symptoms not leading to decreased performance time. Twenty-one dancers from a professional contemporary dance company were followed for 7 weeks. They completed the dance-specific Self-Estimated Functional Inability because of Pain (SEFIP) questionnaire on a weekly basis to quantify musculoskeletal pain. Their TL was calculated by multiplying the Ratings of Perceived Exertion scale (RPE Borg CR10) by the daily training time. Associations between TL and SEFIP scores, recorded on a weekly basis, were evaluated using a mixed linear model with repeated measurements. No significant association was found between TL and severity of musculoskeletal pain. However, the TL of the dancers with no symptoms of overuse-injury, SEFIP = 0, was significantly lower compared to the dancers with symptoms, SEFIP > 0; p = 0.02. No time loss because of injury was reported during the study period. There were 251 symptoms of overuse injury reported, and 67% of the recorded time was danced with pain. It is concluded that dancers without musculoskeletal pain had lower TLs. While no time-loss injuries were found, two-third of the participants danced with pain during this 7-week period.

21

Few studies have investigated how balance is maintained while the body rotates in an upright posture. Under the basic definition of balance, the body’s center of mass (CoM) lies along a vertical line over the base of support (BoS); therefore, balance can be regained by moving the position of the CoM or the BoS. In a ballet pirouette, extreme movement of the BoS is aesthetically unacceptable; however, subtler BoS translations may be a viable strategy for balance maintenance. The results of this study suggest that translation of the BoS is not only utilized but correlated with a larger number of revolutions, n, in a pirouette. Although increasing n is not the primary goal of the pirouette, scientific understanding of how dancers maintain balance while performing large n turns can help dance educators teach safer, more effective pirouettes of any n. To investigate the relationship between the number of revolutions completed in a pirouette and 1. physical properties of the dancers, 2. how the pirouettes were initiated, 3. maximum deviations from equilibrium, and 4. movement of the BoS, this study determined whether n was correlated with several relevant biomechanical parameters. Motion analysis of 11 skilled female dancers performing standard ballet pirouettes determined CoM and BoS kinematics. Six variables were computed from these data: initial topple angle from vertical (4.5° ± 2.0°), initial margin of stability (-4.4 ± 2.8 cm), initial spin rate (2.19 ± 0.37 rev/s), maximum topple angle (9.8° ± 6.8°), normalized BoS distance traveled per revolution (7.3% ± 3.3%), and dancer effective pendulum length (1.172 ± 0.023 m). A significant positive correlation was found between n and normalized BoS distance traveled per revolution (r = .873, p < 0.001). No significant correlations were found between n and any of the other five variables. When the foot rotates against the ground, as in a pirouette, friction is kinetic (lower coefficient of friction than no relative motion between surfaces), and body manipulations for balance maintenance lead to greater likelihood of BoS translation. These results suggest that dancers should be encouraged to make adjustments that could lead to subtle BoS translations during rotations. Given this new information, more research is needed to determine the best practices for teaching balance maintenance during rotations in dance.

0

This randomized controlled trial examined the immediate effect of whole body vibration (WBV) on first position sauté height, and on static and dynamic balance, in 59 female professional contemporary dancers. Following instruction, a warm-up, and a training session, participants received a 75-second randomly assigned WBV intervention under four conditions: static demi-plié (0 Hz), static demi-plié (30 Hz), dynamic demi-plié (0 Hz), and dynamic demi-plié (30 Hz). Before and immediately after intervention, participants performed three sautés on the Just Jump ® Mat System, provided dynamic balance data via the Star Excursion Balance Test, and static balance data via the Balance Error Scoring System. A two-way split-plot multivariate approach ANOVA was used to analyze sauté height (α = 0.025). Balance was examined with a 4 x 2 x 2 split-plot MANOVA (α = 0.025). Follow-up two-way split plot multivariate approach ANOVAs were also conducted (α = 0.0125). Dancers from the static first position demi-plié group were found to jump higher than those from the dynamic first position demi-plié group, regardless of WBV frequency (p = 0.001). The 30 Hz frequency resulted in significantly improved static balance (p = 0.001) for both static and dynamic demi-plié. Therefore, the use of WBV is worthy of consideration as a quick method of improving static balance, and use of the static first position demi-plié may be beneficial for improving sauté height.

0

Belly dance is an appreciably under researched dance form. As such, little is known of the injury prevalence and risk factors for injury among this dance population. Therefore, the primary objective of this study was to examine the most common injury sites and to identify potential factors associated with injury risk within the belly dance community of New Zealand over a 12-month retrospective period. Dancers who had practiced or performed belly dance during that time span were surveyed using an online or paper-based questionnaire. One hundred and nine injury questionnaires (all from female dancers) qualified for the final analysis. The participants had a median age of 44.3 years and danced a median of 3.0 hours per week. The injury rate was 37% (40 injuries in 109 dancers surveyed), the injury incidence proportion was 24.8% (27 dancers reporting at least one injury), and the per hour injury incidence rate was 1.69 per 1,000 dance hours. Of the two most recently sustained injuries reported, lower limb injuries were the most common, followed by trunk injuries. Age, total dance hours per week, and participation in a non-dance exercise regimen of any kind were associated with a decreased risk of injury; performing regularly was associated with an increased injury rate. It is concluded that an understanding of the incidence and sites of injuries may help create awareness that belly dance can be injurious, and subsequently lead to the development of future interventions.

0

In the research devoted to ballet, ground reaction force (GRF) and shoe condition have been identified as possible risk factors for injury. Shoe conditions vary immensely between dancers and could indeed have significant impact on biomechanics and injury rates. Therefore, the objectives of this study were: 1. to investigate the maximal ground reaction force (GRFmax) when ballet dancers land from two jump conditions in pointe shoes, in flat technique shoes, and barefoot; and 2. to explore the effects that specific pointe shoe characteristics (shoe age, shank style) have on GRFmax. Twenty-one healthy female ballet majors in an elite college program volunteered for the study. All participants had similar years of classical ballet training (12.85 ± 2.37). For the study, they performed two ballet jumps, assemblé and grand jeté. Each jump was performed in the three shoe conditions mentioned previously. A total of 18 trials per subject were completed, with the order of jump type and shoe condition randomized. Each jump was landed on a force plate, and maximal GRFs were recorded. A repeated measures analysis of variance was calculated with two within subject factors, shoe type at three levels and jump type at two levels. Tukey’s post hoc test was applied to significant findings. Alpha level was set a priori at p = 0.05. Results demonstrated no significant differences in GRFmax between the three shoe conditions; however, significant differences in GRFmax between the jump types were identified. Post-hoc testing revealed that when dancers performed the grand jeté jump, higher GRFmax was obtained compared to the assemblé jump. In conclusion, results of this study indicate that GRFmax varies between ballet jumps; however, it does not appear that shoe condition significantly affects GRFmax.

0

To progress to a high level in classical ballet, en pointe is a requirement. The aim of this literature review was to evaluate the available evidence relating to readiness for dancing en pointe, including injury rates in the adolescent dancer population, screening tools, and pre-pointe training methods. It has been emphasized that young dancers are a demographic at increased risk of injury, especially as they progress through the growth spurt and increase their training hours. Dancers are commonly screened at the pre-pointe level, but unfortunately the majority of evidence resulting from this process, as reported in the literature, is subjective in nature. Hence, there is large variance regarding an appropriate time or level to commence en pointe training, and it remains unclear what dance teachers should be looking for in making this decision. A further paucity of evidence is demonstrated with regard to pre-pointe training protocols or instruction; in this review, no published literature was found on the topic. As such, there is a clear need for further study of pre-pointe screening and en pointe training protocols.

0

Studies that have investigated the epidemiology of injuries in breakdancing have concluded that the second most common injury site is the knee and that the majority of breakdancers have experienced overuse syndrome. Tendon stiffness, the relationship between force applied to a tendon and the resulting displacement, has been identified as a primary mechanical factor in such injuries. However, patellar tendon stiffness has not yet been evaluated in elite breakdancers. Hence, the purpose of this study was to determine mean patellar tendon stiffness in this population by using myotonometric measurements and to compare those results with healthy control subjects. Twenty-five elite male breakdancers and 25 male control subjects were included in the study. A Myoton Pro device was used to assess their tendon stiffness. The mean patellar tendon stiffness of the breakdancers was 1,045 ± 202 Nm and 1,084 ± 193 Nm for the dominant and non-dominant limb, respectively; for the control group it was 902 ± 166 Nm and 862 ± 159 Nm for the dominant and non-dominant limb, respectively. Statistical analyses showed higher stiffness values for breakdancers compared to controls for both limbs. This is consistent with studies reporting patellar tendon adaptation after training.